Electrical signal amplifying and repeating system



Jan. 20, 1931. v s. F. MIESSNER 1 ,9

ELECTRICAL SIGNAL AMPLIFYING AND REPEATING SYSTEM Filed May 13, 1925 2 Sheets-Shaet 1 INVENTOR flag/0mm [Masner ATTORNE //0V. AC

Jan. 20, 1931.

B. F. MIESSNER 1,789,950

- Filed May 15, 1925 a Sheets-Sheet 2 ATTORN Patented Jan. 20, 19312.. i

umrsn .sTATa-s; ATENT orries 'mmu'mn r. mnssimn, o1- sourn omen, mrw- JERSEY, ASSIGNOB, BY ursm: I assromnrs, T mm CORPORATION or enemas, or NEW YORK, 1w. Y.', a con- PORATION OF- DELAWABE ELECTBICAL SIGNAL AMPLIFYING A JLVD BEPEATING SYSTEM Application filed Kay. 13,

While my invention relates generally to electrical signal amplifying and repeating systems, it is described herein more particularly with reference to such systems used in the reception of high frequency electrical signals,

transmitted through space and over wires, wherein three electrode vacuum tubes are employed as the amplifying and repeating'devices.

An object of my invention is to improve upon the results which have been heretofore obtained when other than steady sources of potential have been employed forenergizing the amplifying and repeating devices to render them operative, particularly where other than steady sources o'f potential are used for energiz mg -the'filament and plate circuits of three electrode vacuumtubes. The invention resides in certaln novel features whereby the humi in the telephones or other translating device resulting from such use of unsteady potentials is materially reduced.

. The art has endeavored to substitute for the battery form of energy supply to" plate circuits of vacuum tubes other sources such as rectified and {filtered commercial 'fre;

' and these ripples become particularly annoy-.

quency alternating currentv and filtered machine generated direct current. No processes of rectification and filtration have as yet been devisedwhich do. not leave subing if the system includes several-stages of audio frequency amplificationto magnify I in',the output end the ripgles in the earlier stages of the system imilar unsteady sources of supply for heating the filaments of vacuum tubes result in a varying difference (if-potential between the grid and filament due to a distributed drop of potential across the filament as well as 'a varying filament to varying electron filament, this latter efiect the case of filaments designed for high temperature operation. These filament effects also manifest themselves as-"variations or ripples in the plate current'of the tube and are available for magnification if *the system includes fication'.

'panying -.drawings, wherein,

1925. s rial. No. 29,859. multiple stages of audio; frequency ampli- A vacuum tube amplifying system including such sources of energysupply invariably suffers from an annoying hum in the telephones or loud speaker characteristic of the variations inthe source'of supply. There are many practical and economical advantages in substituting the hereinbefore battery form nowin most extensive use, and it is an object of my inventionto'eliminate in a. practical sense or decrease the hum creat- 'mg will be no annoying hum. a

I have found thatthe-hum may be most effectively eliminated to practical extents by independently creating ripples or current variations of similaf characteristics and like values to those. created, in system through using the aforementioned unsteady sources of supply, and then balancing the one set of variations by the other. The manner in which I accomplish this result and other novel features of my invention will be best understood the following descripcurrents to such an-ext'ent' that there i l the amplifying v tion taken inconjunctlon with the ac'comr F 1g; 1 is a circuit diagram. of a vacuumtube system employing my invention and illustrated. in use asa receiverfof' high frequency currents transmitted over wires, and A ig. 2 is another circuit diagram of a vacuum tube systemillustrated in use as a radio receiving'system, and in which a single vacuum tube functions both as 'abalancer and as an amplifier, aniadditional feature of my invention.

"In Fig. 1, 1 and 2 represent two wires of an i alternating current power line across which 1s connected .the

rlmary windin 3 of a transformer, whim transfornier as four secondary windings, 4, 5, 6 and (I, respectively. Winding 7 has at least half the number of turns of windin wound in an electrically opposed sense to 6 so that the potential at the terminal 7 is always substantially the same as. the midpoint potential of the winding 6. v Across, the power lines. 1, 2 there is shown connected a high frequency path including a condenser 6 and is also preferably Y 8, which may or'may not be variable, and the primary winding 9 of a radio frequency transformer, the secondary of which is included in the detector circuit 10 comprising a detecting device 11, variable condenser 12 and primary winding 13 of an audio frequency transformer 14:. Hi h frequency carriercurrent, modulated in accordance with signals to be transmitted, is impressed upon the power lines at the central power station, or sub-station-irrespective of low frequency power current-and is thus conveyed up to and through the primary winding 9 whence it is induced into the secondarv 15 of-the detector circuit 10. The modulated high frequency current is acted upon in the usual way in the detector circuit to produce audible frequency current efi'ects characteristic of the modulations, the latter being induced through audio frequency transformer 14 to the input circuit of vac uum tube amplifier 16, wherein they are amplified'and passed through audio frequency transformer 17- into the second audio frequency amplifier 18, the output circuit of which includes a loud speaking or other translating instrument 19.

Vacuum tube 20 functions as a creator of current variations for neutralizing or partially neutralizing the low frequency fluctuations in the output of vacuum tube 16 due to the use of alternating current filament supply and rectified alternating current plate supply all in a manner more fully described.

It will be noted that filaments 21', 22 and 23' of vacuum tubes 16, 18 and 20, respectively are all connected in parallel to the terminals of secondary winding 6 of the power transformer. The filaments are therefore supplied with alternating current of low frequency.

The plate circuits of the three vacuum tubes are supplied with unidirectional fluctuating current derived from rectifying and filtering alternating current, there being provided a rectifier 24, which may be a vacuum tube, or any-other suitable rectifier or rent is filtered or smoothed out to.form an approximationto a continuous current is illustrated as comprising three shunt condensers 26. 27 and 28 and a series resistance 29. "Any suitable form of filter may be employed.

Primary winding 30 of audio transformer 17 is included in the output circuit of vacu um tube 16 and primary winding 31 of trans- 7 former 32 is included in the output circuit of tube 20. Both transformers act on the input circuit of vacuum tube 18. The windings of transformers 17 and 32 are arranged so that currents arising in their respective tubes 16 and 20 act differentially on the input circuit of vacuum tube 18.

\Vith the desired signal currents impressed upon the input circuit of vacuum tube 16 and tothe exclusion of tube 20 there is no cancella- 30 tion or opposing of these desired currents during their input from tube 16 to tube 18, and.,they therefore go through the system and are amplified for use in the translating device 19. If however, vacuum tube 20 ischosen to have substantially the same characteristics asvacuum tube 16, and bein as illustrated, excited in both plate and filament circuits fromthe same sources as tube 16, then there are created like variations other than signal currents to those in tube 16 which oppose or cancel on input to tube 18.

I have not shown a balancing tube provided for the second amplifier tube 18 because I have found in practice that the second balancer may be omitted without the bum becoming over-objectionable. In the first place variations arising in this last tube are not furtheramplified to the same extent as would be unneutralize'd variations arising in preceding tubes and passed 011 to this last tube. Also a slight overbalance may be accomplished in the preceding tube, the'residual being uti-' lizedto balance undesired variations in the last tube and, being amplified, only a small 10 over-balance or residual is needed to balance much larger variations in the last tube. Such an overbalance, and the phaseof it, may be accbmplished by interchanging tubes 16 and 20, as it would be rare to find two tubes exact- 1y alike, or adjusting the potentiometer 37 from which wire 35 leads to the grids of tubes 16 and 18. This adjustment changes the alternating current potential on the grids, but since the grid of tube 16 is excited through secondary winding of transformer 14 and the grid of tube 20 is in a non-reactive lead, there would result a difference in grid effects sufficient to bring about an over-balance. Of

course, other suitable devices for adjustment -well within the skill of the art may be included in the system. The result of such overbalance is to impress on the grid of tube 18 variations in potential which reduce or neutralize variations in the plate circuit of tube 18 that are caused by the varying potential supplied by the rectifier and filter, and by the alternating heating current in the filament of tube 18. Or a balancer tube may be used in con] unction with tube 18 in the same mannei 'a's illustrated fortube ltiif a great nicety of balance-in the 'systemisrequired, but for ordinary practice a-small amount of hum is not objectionable, being completely masked by any signal of fair intensity.

A grid biasing battery 38 may or may not be employed.

A groundv connection is often found desirable. For the purpose of grounding the circuit a two-way switch 39 is provided, one contact of which goes directly to ground and the other through a condenser 40to the grounded side ofthe power transmission line. It is contemplated that whichever ground connection 'ves the better result, in any instance, woul beused; 1

Fig. 2 illustrates an arrangement embodymg my invention more'par ticularly adapted for radio reception,

and wherein I employ a vacuum tube in the dualcapacity of balancer and amplifier. In the system of Fig. 2 modulated high frequency currents are collected by the antenna 41- and passed through radio frequency transformer 42 to the tuned v input circuit 43 of a radio frequency amplifier tube 44. The output circuit of amplifier tube 44 includes the primary winding 45 of a Y The input circuit v 51, in the input circuit of athird amplifier tube -52. The radio frequency output 0 amplifier tube 52 is impressed through transformer 53 upon. a detector circuit 54 which includes a crystal or other detector 55. The detector circurrent.

cuit functions in theusual manner to convert the amplified radio frequency current into audio frequency efl'ects corresponding t'o'the modulations. The detected audio frequency modulations are passed through the primary winding 56 of an audio frequency transformer 57 and impressed upon the input circuit of tube 47 which, as was shown, also functions as a radio requeney amplifiertube, This tube also functions as the first audio amplifier and includes in its output circuit, the -primary winding 58 of an audio frequency transformcr 59. The audio are thus impressed upon frequencyamplifier. The

device 61 which is shunted by .a condenser 62 forming a Tube 44 functions as the -balancer for the first audio frequency st e tube 47 in the same manner as was describe in connection with U fere with its quency output 7 amplifier, a etector,

quenc frequency currents pass fi from the primary 58 to the secondary of' transformer 59 and the input. circuit of amplier tube 52 which also. functions as a radio output circuit of tube 52 includes a translating sources of potential, means by-pass forthe radio frequency 1 for returning and passing th Fig. 1-. This role-ofbalancer does not inter other function in the system, thatof radio ance is secured through winding 63 in the plate circuit of tube 44acting differentially or oppositely to winding 58 in the platecircuit oftub'e47.

As described in connection withF ig. l,-an

frequency-r amplifier. The baladditional 'balancingtube may be provided for balancing out tube 52, but as ex the description 0 easily be balanced out or 'satisfactorily reduced by hum current energy coming from the preceding tubes.

for the plate supply and heating-the filaments with alternating currents are identical with thought scribed, but only by the scope of the appended the hum arising in' vac'uum lained in connection with f the circuit of Fig. 1, the hum is not usually regarded as excessive withv the second balancing tube omitted, and "may many different circuit" The provisions in Fig. 2 for convertingalternating current into umdirectiona'l current the output of one or more of the repeaters of the low, frequency portion by the low freenergization of one or more of the repeaters of the high frequency portion. I

I 2. A system adapted to amplify high frequency currents. modulated at lower signalto fluctuating potential ing frequenc including a high frequency operation from fluctuating-sources of potential'and means for opposing-the output of the a low frequency amplifier, means for'energiz'ing the amplifiers for low frequency amplifier with thelow' freoutput due'to fluctuating potential energlzation ofthehighfrequency amplier. I I

3. A systemadapted to amplify high frequency electrical currents" modulated at lower signaling frequency including amplifying repeaters, means for energizing-the repeaters for operation from fluctuating for employing the repeaters as amplifiers of the currents in high frequency form, means for converting the high frequency current rents of the lower signaling frequency, means low frequency energy to" curoutput due to fluctuating potential energization of the non-low frequency signal current excited repeaters. i

4. In a Wave signal receiving system, a pair of three-electrode vacuum tubes each comprising a filament, a grid and a plate, a source of alternating filament heating current connected to said filaments, output circuits for said tubes, said output circuits being diflerentially related in such manner that equal and simultaneous space current Variations in said tubes oppose and substantially cancel each other out and means whereby both of said tubes are rendered operable as radio frequency amplifiers and one of said tubes is rendered operable as an audio frequency amplifier.

5 A signal current amplifying system employing a plurality of three-electrode "acuum tubes arranged for multi-stage amplification of signaling current, a source of current supply for energizing. a' circuit of each of said tubes and tending to cause periodic disturbing variations in the plate circuit of said tubes, a coupling between the plate circuit of one of said tubes and the grid circuit of another of said tubes, said coupling being so arranged that variations produced in the grid circuit by variations in the plate circuit which is coupled thereto neutralize the variations in the plate circuit ofsaid other tube.

6. In a signal current amplifying system employing three-electrodevacuum tubes the plate circuits of which are subject to current variations of similar frequency and phase, means for reversing the phase of such variations in the plate circuit of one of the tubes and ap'plyingthe reverse variations to the arid circuit of another of the tubes, and adjustable means for altering said reverse variations, said-'means including a circuit for supplying alternating current for heating the tube filaments and an adjustable connection between the grids of said tubes and points of different potential of said supply circuit.

7. In a signal amplifying system, a pair of three-electrodevacuum tubes, means for exciting-one of the circuits of each tube with current at a potential which varies at audio frequency, thereby tending to produce in the plate circuits of said tubestlisturbing variations of current at a corresponding frequency,

and an audio frequency coupling between the grid circuit of one-tube and the plate circuit of the other tube, said coupling being so arranged that the disturbing current variations in the plate circuit of said other tube are impressed on the grid circuit of said one tube in such a way as to neutralize the disturbing current variations in the plate circuit of the one tube.

8. In an electrical signal amplifying system, a pair of three-electrode vacuum tubes,

,an audio frequency coupling between the grid circuitof one of the tubes and the plate circuit of the other tube, one of said tubes having an inductive and the other of said tubes having a non-inductive grid circuit, a circuit for supplying alternating current to the filaments of said tubes for heating. the same, and a connection between said grid circuits and said supply circuit, said connection being adjustable to points of different potential of said supply circuit, which points. are in the neighborhoodof the point of zeropotential of said supply circuit.

9. In a signal current amplifying system employing three=electrode vacuum tubes arranged for multi-stage amplification of signaling'current, means for energizing each of said tubes for operation from a common source of current energy tending to cause. periodic disturbing variations in the plate circuits thereof, means for passing to the grid circuit of a succeeding tube some of the disturbing energy of a preceding tube of phase to oppose the disturbing energy in the plate circuit of said succeeding tube,, and

means for proportioning said passed energy in accordance with the amplification of said succeeding tube to substantially neutralize the disturbing energy in the plate circuit thereof.

10. In a signal current amplifying system employing three-electrode vacuum tubes arranged for multi-stage amplification of signaling current, means for energizing each of said tubes for operation from a common source of current energy tending to cause periodic disturbing variations in the platecircuits thereof, and connected to produce said variations in like phase, and means for passing to the grid circuit of one of said tubes some of the. disturbing energy of anize the disturbing variations in the plate circuit of said first tube.

' 11. In an audio frequency signal current amplifying system employing three-electrode vacuum tubes arranged for multi-stage amplification, means for energizing each of said tubes for operation from a common source of commercial alternating current energy tending to cause periodic audio frequency disturbing variations in the plate fer disturbing current energy 0 a preceding tube to neutralize disturbing current energy of a. succeeding tube.

12. In a signal current amplifying system for other one of said tubes of phase to neutralenergy from energy from I grid circuit of another'one of saIdtubes to oppose the energizin current fluctuations m.

trodes of each of said accordance with said ampli 17. In a signal current amplifying sysfor energizing each of said tubes at least in part for operation from a common source" alternating current connected to. said tubes so that the disturbing variations are produced in like phase, and means for passing energizing energy I through the grid circuit of anotherone ofsa'id tubes in a' phase to oppose the energizing fluctuations. said other tube.

13. In a signal current amplifying s stem employing three-electrode vacuum tubes arranged for multi-stage amplification, means for energizing for operation like electrodes of each of said tubes from a common source of connectedto said electrodes-so that the disturbing variations are produced in like .phase, and means for passing energizing fluctuating grid circuit of another one of said tubes in a phase to opposethe energizing current fluctuations in the plate circuit of said other tube.

14. In a signal currentampli'fying system employing three-electrode vacuum tu es arranged for multi-stageamplification, means for energizin for operation like electubes from a common source of periodically fluctuating current, and means for passing energizing fluctuating one of said tubes through the the plate circuit 0 said I other tube, and means proportioning the amount of said energy so passed to the energy in the plate c 1r,- cult of said other tube in accordance with the amplification of said other tube.

pair of three-electrode vacuum from one of said tubes in the V plate circuit of periodically fluctuating, current one of said tubes through the the plate 'turbing energy of another tions in the plate circuit of In a signal current amplifying system employinga tem including 'three-electrodevacuum tubes,-

means for neutralizing fluctuating compo- ;nents' of said energy'in said audio frequency portion with fluctuating energy derived from the energizing energy of saidradio frequency I portion.

.18. In a signal current amplifying system including a plurality of three-electrode vacuum tubes connected in cascade to amplify [audio frequency currents, means for ener-' of saidtubes for opj gizing like electrodes eration from a common source of periodically fluctuating current energy .connected to said electrodes so that the disturbin varia tions are produced in like phase, an means for neutralizing fluctuating ,components of said energy one of said tubeswith fluctua common source ofpemeans for employing some of said tubes as radio frequency amplifiers and some of said atlng energy';-derivedifr'om the energizing I energy ofanother of said tubes.

19. In a signal current amplifying system employing three electrode vacuum tubes arranged for multi-stage amplification of sig naling current, means connecting the fila ments of said tubes in parallel to a common source of resulting periodic disturbing variations in.

. alternating current, whereby'the circuits of said tubes are of like phase, and means for passing to the grid circuit of one of. said tubes some of the disone of said tubes disturbing varia- Said first tube.

1 In testimony whereof I aflix my signature. BENJAMIN FIMIESSNER.

of phase to neutralize the tubes arranged for multi-stag e amplification v v and having like electrodes ener 'zed for oferation from a common source 0 periodical v fluctuating current, the method of reducing hum disturbances which consists of opposing the fluctuations of energizing current in one of said tubes by lesser, fluctuations derived from another of saidtubes tion at least by said first tube.

16. In a signal current amplifying system" after amplificaemploying three-electrode vacuum tubes arranged for m'ulti-s'tage amplification and having like electrodes energized for o eration from a common source of periodically fluctuating current, the methodof reducing hum disturbances which consists of opposing the fluctuations of energizing current in one of said tubes byfluctuations derived. from another of said tubes and amplified at least by said first tube, and proportioningsaid derived ene'r to said op energy 1n catlon.

DISCLAIMER 1,78l,950.Bnjamin F. Miessner, South Orange, N. J. IELECTERICAL SIGNAL AMPLI- ,FYING AND REPEATING SYSTEM. Patent dated January 20, 1931. Disclaimer filed January 20, 1932, by the assignee, Radio Corporation of America. I

Hereby enters this disclaimer to the said claims of said Letters Patent which are in the following Words, to wit:

Claim 5: A signal current amplifying system employing a plurality of three-electrode vacuum tubes arranged for multi-stage amplification of signaling current, a source of current supply for energizing a circuit of each of said tubes and tending to 1 cause periodic disturbing variations in the plate circuit of said-tubes, a coupling between the plate circuit of one of said tubes and the grid circuit of another of said tubes, said coupling being so arranged that variations produced inthe grid circuit by variations in the plate circuit which is coupled thereto neutralize the variations in the plate circuit of said other tube. I

-' Claim 10:' In a signal current amplifying system employing three-electrode vacuum tubes arranged for'multi-stage amplification of'signaling current, means for energizing each of said tubes for operationfrom a common source of current energy 1 tending to cause periodic disturbing variations in the plate circuits thereof, and con- 7 nected to produce said variations in like phase, and means for passing to the grid circuit of one of said tubes some of the disturbing energyof another one of said tubes of phase to neutralize the disturbi.ng variations in the plataclrcuit of said first tube. Claim 11: In an audio frequency slgnal current amphfying system employing three-electrode vacuum tubes arranged for multi-stage amplification, means for energizing each of said tubes for operation from a common source of commercial alternating current energy tending to cause per1od1c audio frequency disturbing variations in the, plate circuits thereof, and connected to produce said variations in like phase,

means for transferring signal current energy and disturbing current energy from one tube to another; said means being arranged to transfer disturbing current energy of a preceding tube to neutralize disturbing current energy of a succeeding tube.

- .Claim 12:In a signal current amphfymg system employing three-electrode vacuum tubes arranged for multi-stage amplification, means for energizing each of said tubes at least inpart for operation from a common source of alternating current connected to said tubes so that the disturbing variations are produced in like phase, and means for passing energizing energy from one of said tubes through the grid circuit of another one of said tubes in a phase to oppose the energizing fluctuations in the plate circuit of said other tube.

' Claim 13: In a signal current amplifying system employing three-electrode vacuum tubes arranged for multi-stage amplification, means for energizing 'for operation like electrodes of each of said tubes from a common source of periodicallyfiuctuating current connected to said electrodes so that the disturbing variations are produced in like phase, and means for passing energizing fluctuating energy from one of said tubes through the grid circuit of another one of said tubes in a phase to oppose the energizing current fluctuations in the plate circuit of said, other tube.

Claim 15: In a signal current amplifying system employing a pair of three-'elec-.

trode vacuum tubes arranged for multi-stage amplification and having-like electrodes energized for operation from a common source of periodically fluctuating current, the

method of reducing hum disturbances which consists of gopposing. the fluctuations of energizing current in one of said tubes by lesser fluctuations derived fromanother of i said tubes after amplification at least by said first tube.

Claim 18: In a signal current amplifying system including a plurality of threeelectrode vacuum tubes connected in cascade to amplify-audio frequency currents,

I means for energizing like electrodes of said tubes for operation from a common source of periodically fluctuating current energy connected to said electrodes so that the d'isturbing variations are produced in likephase, and means for neutralizing fluctuatingcomponents of said energy in one of said tubes with fluctuating energy derived. 1 from the'energizing energy-of another of said tubes.

3 "Your petitioner hereby enters this disclaimer to the combination covered by claim 7 ofsaidjpatent aforesaid except when a single audio frequency coupling is used between the grid circuit of one tube and the plate circuit'of the other tube for transmitting both signal currents and disturbing current variations.

' I Gazette March 1, 1932.] 

